Anisotropy and Microcrack Propagation Induced by Weathering, Regional Stresses and Topographic Stresses

Xu, Tingting; Shen, Xianda; Reed, Miles; West, Nicole; Ferrier, Ken L.; Arson, Chloé

doi:10.1029/2022jb024518

Cited by 4 publications

(1 citation statement)

References 73 publications

(138 reference statements)

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“…Biotite expansion generates new fractures, providing more mineral surface area for geochemical reactions (Bazilevskaya et al., 2013; Buss et al., 2008; Tian et al., 2019) and sufficient energy density to fracture rock over cm length scales in granites (Goodfellow et al., 2016; Goodfellow & Hilley, 2022). The stresses created by biotite expansion can impact the state of stress on the hillslope scales (Shen et al., 2019; Xu et al., 2022). The low effective pressures in the CZ (<1 MPa) allow fractures created by biotite to remain open.…”

Section: Discussionmentioning

confidence: 99%

Low V_p/V_sValues as an Indicator for Fractures in the Critical Zone

Flinchum,

Grana,

Carr

et al. 2024

Geophysical Research Letters

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Poisson's ratio for earth materials is usually assumed to be positive (Vp/Vs > 1.4). However, this assumption may not be valid in the critical zone because near Earth's surface effective pressures are low (<1 MPa), porosity has a wide range (0%–60%), there are significant texture changes (e.g., unconsolidated vs. fractured media), and saturation ranges from 0% to 100%. We present P‐wave (Vp) and S‐wave (Vs) velocities from seismic refraction profiles collected in weathered crystalline environments in South Carolina and Wyoming. Our data show that ∼20% of the subsurface has negative Poisson's ratios (Vp/Vs values < 1.4), a conclusion supported by borehole sonic logs. The low Vp/Vs values are confined to the fractured bedrock and saprolite. Our data support the hypothesis that weathering‐generated microcracks can produce a negative Poisson's ratio and that Vp/Vs values can thus provide insight into important critical zone weathering processes.

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Section: Discussionmentioning

confidence: 99%

Low V_p/V_sValues as an Indicator for Fractures in the Critical Zone

Flinchum,

Grana,

Carr

et al. 2024

Geophysical Research Letters

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Impact of stylolite cementation on weathering rates of carbonate rocks

Israeli,

Emmanuel

2023

Carbonates Evaporites

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The weathering of carbonate rocks plays a signi cant role in the evolution of Earth's surface. Such weathering is often accelerated by the presence of stylolites, which are rough, serated surfaces that form by dissolution under burial or tectonic stresses. Stylolites are thought to represent zones of mechanical weakness in rocks, as well as regions in which chemical weathering is enhanced. However, a quantitative framework capable of predicting how stylolites accelerate weathering in carbonates has yet to be achieved. In this study, we rst used scanning electron microscopy and wavelength dispersive spectroscopy to characterize the way in which the two sides of individual stylolites are connected at the microscopic scale. In the samples we examined, we found that micrometer-scale calcite bridges span the opposing sides of the stylolites, effectively cementing the rock together. This cement lled 1%-30% of the stylolite volume. We then used a numerical cellular automaton model to simulate the effect that the degree of carbonate cementation has on stylolitic carbonate rock weathering. Our results show that weathering rates decrease non-linearly as the degree of stylolite cementation increases. The effect on overall rock weathering rates is signi cant: stylolite-bearing rocks with 1% cementation weathered as much as 37 times faster than limestone without stylolites, primarily because of accelerated mechanical erosion. Our results indicate that stylolites could be as important as joints and fractures in accelerating carbonate rock weathering and in the development of karst landscapes, potentially making a major contribution to global carbonate weathering.

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